Rheology of dense granular flow: from dry to suspended systems

Jin Sun (The University of Edinburgh)

Frank Adams 1, Alan Turing Building,

Flow of densely packed granular particles is ubiquitous in nature
and industry, such as debris flow, pastes and slurry flows. In this talk, I
will present a unified flow regime map for both dry and suspended dense
granular flows, with an emphasis on the relationships between bulk rheology
and particle-scale phenomena. We investigate the rheology using discrete
element method simulations of homogeneous, simple shear flow of soft,
frictional, spheres, taking particle contact and/or hydrodynamic lubrication
into account. For steady shear flow, we delineate viscous, inertial and
quasistatic bulk rheology as a function of Stokes number and volume
fraction. Transitions in microscopic phenomena, such as interparticle force
distribution, fabric, and correlation length are found to correspond to
those in the macroscopic flow. The unsteady flow behaviour is probed by
studying their response to shear reversal, observing salient feature of
stress evolution, which can be related to microstructure evolution. I will
also present constitutive models that can capture the transitions between
steady shear flow regimes and the microstructure evolution.

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